In the field of digital communications, in particular digital Radio Frequency (RF) communications, there is a need for secure and reliable communications. The Universal Mobile Telecommunications System (UMTS), a 3rd Generation communications system developed by the 3rd Generation Partnership Project (3GPP), employs a so-called “f8” confidentiality algorithm and a so-called “f9” integrity algorithm, for example as described in 3GPP TS 35.202 (v4.0.0 (2001-08), Document 2: KASUMI Specification (Release 4)). Both the “f8” and “f9” algorithms are based upon a Kasumi algorithm, which evolved from a so-called “Misty1” crypto algorithm developed by Mitsubishi Electronic Corporation, Japan.
The Kasumi algorithm is an 8-round Feistel block cipher that encrypts a 64-bit plaintext input into a 64-bit ciphertext output. Kasumi encryption and/or decryption is performed by wireless handset units and by Radio Network Controllers (RNCs) in the UMTS. Implementation of the Kasumi algorithm is becoming both increasingly important, and increasingly difficult with the introduction of High Speed Downlink Packet Access (HDPA) services, which places an even greater data throughput requirement, and hence performance burden, on the RNC that at present.
In this respect, the Kasumi algorithm was developed with an expectation that the algorithm would be executed on a 16-bit processors, execution of the algorithm in its current form being incompatible with other, more powerful, processors, such as 32-bit processors.